Single-Layer Sensor Stack

ABSTRACT

In one embodiment, an apparatus includes an adhesive layer between a cover panel and a substrate. The substrate has drive or sense electrodes of a touch sensor disposed on it. The drive or sense electrodes are made of a conductive mesh of conductive material including metal.

RELATED APPLICATION

This application is a continuation under 35 U.S.C. §120 of U.S. patentapplication Ser. No. 12/608,779, filed Oct. 19, 2009.

TECHNICAL FIELD

This disclosure generally relates to touch sensors.

BACKGROUND

Touchscreen displays are able to detect a touch within the active ordisplay area, such as detecting whether a finger is present pressing afixed-image touchscreen button or detecting the presence and position ofa finger on a larger touchscreen display. Some touchscreens can alsodetect the presence of elements other than a finger, such as a stylusused to generate a digital signature, select objects, or perform otherfunctions on a touchscreen display.

Use of a touchscreen as part of a display allows an electronic device tochange a display image, and to present different buttons, images, orother regions that can be selected, manipulated, or actuated by touch.Touchscreens can therefore provide an effective user interface for cellphones, GPS devices, personal digital assistants (PDAs), computers, ATMmachines, and other devices.

Touchscreens use various technologies to sense touch from a finger orstylus, such as resistive, capacitive, infrared, and acoustic sensors.Resistive sensors rely on touch to cause two resistive elementsoverlaying the display to contact one another completing a resistivecircuit, while capacitive sensors rely on the capacitance of a fingerchanging the capacitance detected by an array of elements overlaying thedisplay device. Infrared and acoustic touchscreens similarly rely on afinger or stylus to interrupt infrared or acoustic waves across thescreen, indicating the presence and position of a touch.

Capacitive and resistive touchscreens often use transparent conductorssuch as indium tin oxide (ITO) or transparent conductive polymers suchas PEDOT to form an array over the display image, so that the displayimage can be seen through the conductive elements used to sense touch.The size, shape, and pattern of circuitry have an effect on the accuracyof the touchscreen, as well as on the visibility of the circuitryoverlaying the display. Although a single layer of most suitableconductive elements is difficult to see when overlaying a display,multiple layers can be visible to a user, and some materials such asfine line metal elements are not transparent but rely on their smallsize to avoid being seen by users.

Further, touchscreens are often used to overlay displays such as LCDdisplay screens that have their own circuitry and patterns. It istherefore desirable to consider the configuration of touchscreenelectrode patterns when designing a touchscreen.

SUMMARY

A touchscreen includes touchscreen electrode elements distributed acrossan active area of a substrate, and the touchscreen overlays a display.The touchscreen electrode elements are configured to avoid creatingmoiré patterns between the display and the touchscreen, such as angled,wavy, zig-zag, or randomized lines. In a further example, the electrodesform a mesh pattern configured to avoid moiré patterns.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a two-layer mutual capacitance touchscreen assembly,consistent with the prior art.

FIG. 2 illustrates a variety of touchscreen element patterns designed toreduce moiré effect when overlaying a display, consistent with anexample embodiment.

FIG. 3 illustrates a two-layer touchscreen assembly comprisingrandomized electrodes configured to reduce moiré effect when overlayinga display, consistent with an example embodiment.

FIG. 4 shows a two-layer touchscreen display assembly comprisingoverlapping drive and receive mesh electrode patterns configured toreduce moiré effect when overlaying a display, consistent with anexample embodiment.

FIG. 5 shows a self capacitance touch sensing system, consistent with anexample embodiment.

FIG. 6 shows a mutual capacitance touch sensing system with a fingerpresent, consistent with an example embodiment.

FIG. 7 shows a single layer touchscreen assembly overlaying a LCDdisplay panel according to an example embodiment.

FIG. 8 shows an exploded view of a dual layer touchscreen assemblyoverlaying a LCD display panel according to an example embodiment.

FIG. 9 shows the assembled dual layer touchscreen assembly of FIG. 8according to an example embodiment.

FIG. 10 shows a cellular telephone having a touchscreen displayaccording to an example embodiment.

DETAILED DESCRIPTION

Touchscreens are often used as interfaces on small electronic devices,appliances, and other such electronic systems because the display behindthe touchscreen can be easily adapted to provide instruction to the userand to receive various types of input, thereby providing an intuitiveinterface that requires very little user training to use effectively.Inexpensive and efficient touchscreen technologies enable incorporationof touchscreens into inexpensive commercial devices, but theseinexpensive technologies should also desirably be durable and haverelatively high immunity to noise, moisture or dirt, or other unintendedoperation to ensure reliability and longevity of the touchscreenassembly.

In a typical mutual capacitance touchscreen, the capacitance betweendrive electrodes and various receive or sense electrodes is monitored,and a change in mutual capacitance between the electrodes indicates thepresence and position of a finger. Mutual capacitance sensor circuitrymeasures the capacitance between the drive electrodes and the receiveelectrodes, which are covered by a dielectric overlay material thatprovides a sealed housing. When a finger is present, field couplingbetween the drive and receive electrodes is attenuated, as the humanbody conducts away a portion of the field that arcs between the driveand receive electrodes. This reduces the measured capacitive couplingbetween the drive and receive electrodes. In a self-capacitancetouchscreen, an array of a single type of electrode is used to determineposition of a touch by monitoring the touch's influence on theself-capacitance of each of the electrodes in the array. The attachedcircuitry can measure the self capacitance of a single electrode, or ofgroups of electrodes such as rows and columns of electrodes. In a moredetailed example, an amount of charge needed to raise the voltage of theelectrode by a predetermined amount is measured, thereby determining thecapacitance of each electrode. When a finger is present, theself-capacitance of the electrode is increased, resulting in ameasurable change in self-capacitance.

The touchscreen elements that overlay a display are occasionally formedfrom conductive materials such as metal wire traces or fine line metal,or more commonly conductors such as Indium tin oxide which aretransparent and relatively conductive in thin layers. Other materialssuch as PEDOT (polyethylene dioxythiophene) and other conductivepolymers are also relatively transparent and used in some touchscreens.

An example touchscreen shown in FIG. 1 uses an array of conductivetraces as touchscreen elements, having X drive and Y receive lines indifferent layers when operated in a mutual capacitance mode. Inself-capacitance operation, the self capacitance of the X and Yelectrodes are independently determined to determine the position of thefinger in two dimensions. The elements in this example are distributedacross the touchscreen display approximately evenly, and are dividedinto different zones 0-3 for both the X drive and Y receive lines. In amore detailed mutual capacitance example, four different drive signalsX0-X3 drive the four separate arrays of horizontal X drive lines, asshown generally at 101. The signals driving these lines capacitivelycouple with the vertical receive lines Y0-Y3, shown at 102. When afinger 103 touches the touchscreen, the finger desirably interacts withseveral X drive lines, intersecting the X0 and X1 drive lines such thatthe finger's position on the touchscreen can be determined by the degreeof interference with capacitive coupling of each drive and receive zone.

In this example, the finger 103 interferes with capacitive couplingbetween the X0 and X1 drive lines and the receive lines approximatelyequally, and similarly interferes with the capacitive coupling betweenthe Y2 and Y3 receive lines and the X drive lines approximately equally.This indicates that the finger's touch is located between X0 and X1, andbetween Y2 and Y3 on the grid formed by the drive and receive lines.

Although each zone in this example comprises multiple electrodes, inother examples each zone may have a single electrode, at the cost of agreater number of electrical connections to the touchscreen. Thetouchscreen display of FIG. 1 is here shown having four differentvertical regions and four different horizontal regions, but otherembodiments such as a typical computer or smart phone application mayhave significantly more zones than shown in this example.

Because the finger touch 103 is somewhat round or oval in shape, it willinteract more strongly with drive lines near the center of the fingerthan at either the top or bottom extreme edge of the fingerprint.Further, the finger will interact to a lesser degree with adjacent driveand receive lines not directly under the area of physical contactbetween the finger and the screen's protective layers, where the fingeris still physically near enough the drive and receive lines to interactwith their capacitive coupling.

The finger's influence on multiple drive and receive lines enables thetouchscreen display to detect the vertical and horizontal position of afinger on the touchscreen display with very good accuracy, well beyondsimply determining in which of the four shown vertical and horizontalregions the finger is located. To achieve this result, the line spacinghere is configured anticipating a fingerprint that is approximately 8 mmin diameter. In this example, the lines are spaced approximately 2 mmapart, for a 6 mm electrode pitch, such that a typical touch interactsstrongly with at least three or four vertical and horizontal lines.

In operation, a user of the touchscreen display of FIG. 1 places afinger on or near the touchscreen as shown at 103. In mutual capacitancemode, series of pulses are sent via the X0-X4 drive lines, such that themutual capacitance between the different X drive lines and Y receivelines can be separately determined, such as by observation of a changein received charge or another suitable method. When the presence of afinger interrupts the field between the X and Y drive and receive lines,such as by coming in close proximity to a portion of the touchscreen, areduction in observed field coupling between the electrodes is observed.

The distribution of lines across the touchscreen display is alsogenerally uniform, resulting in relatively uniform brightness across thetouchscreen display. But, the regular pattern and spacing of lines suchas in FIG. 1 can cause interference with the regular, repeating pixelpattern of a display, causing visible moiré patterns that distort orreduce the clarity of an underlying displayed image.

Configuration of touchscreen elements relative to the line or pixelconfiguration of a display assembly is therefore important in someapplications to reduce moiré patterns, as line configurations that coverregular or repeating patterns of pixels can create interference or moirépatterns in the touchscreen display assembly. It is therefore desirablein some embodiments to configure electrodes in an embodiment such asthat of FIG. 1 to be irregular or at angles that do not cause suchinterference with the underlying display assembly.

The line configuration in touchscreen displays in some exampleembodiments of the invention is determined to avoid creatinginterference or moiré patterns as a result of the line geometryinteracting with the pixel geometry of the display. For example, linesthat are very near but slightly offset from a line angle of the display,such as one degree, are likely to produce interference patterns.Similarly, right angles or fractions thereof such as 90 degree angles,45 degree angles, and 22.5 degree angles may also be more likely toproduce moiré patterns depending on the configuration of the displayelements and the line pitch of the touchscreen element.

FIG. 2 shows several examples of touchscreen elements configured toreduce or eliminate interference patterns, consistent with variousexample touchscreen embodiments. Touchscreen elements such as these canbe substituted for the straight fine line metal elements of FIG. 1,reducing moiré pattern visibility in a touchscreen assembly.

At 201, the lines are configured at an angle rather than square to anedge of the touchscreen display assembly and LCD display, reducing thelikelihood of interference patterns. At 202, wavy lines are used toavoid long linear stretches of fine metal line, reducing the probabilityof causing interference patterns. Similarly, the fine metal lines at 203zig-zag, breaking up long linear stretches of parallel lines. At 204,the lines follow a randomized pattern, and so also lack long linearportions. A randomized electrode pattern is also shown at 205, but therandomized electrode line is shifted laterally from line to line tobreak up vertical regularity in the electrode pattern; the amount ofshifting from line to line can in itself be randomized to furthersuppress the ability of groups of lines to cause a moiré effect.Fractal-based or other irregular shapes are used in further embodimentsto achieve a similar effect.

Although angled and wavy lines are used here to avoid creating moirépatterns, a variety of factors other than angle or direction of thelines will affect the likelihood of observing a moiré pattern whenoverlaying a display with a touchscreen assembly, including touchscreenelement or electrode line width, frequency, and scale. In someembodiments, the touchscreen elements are formed using fine line metalon the order of 3-7 micrometers in width, which is much smaller than thetypical pixel size of even high resolution LCD displays.

A high resolution LCD display pixel is typically made up of threeindividual red, green, and blue sub-pixels that are 100-150 micrometersin diameter, or 0.1-0.15 millimeters. This large difference in scalereduces the amount that a line can overlap a pixel, limiting the amountthe pixel's apparent brightness can be attenuated by the overlappingtouchscreen. Because the difference between sub-pixels obscured byoverlapping touchscreen lines and sub-pixels not obscured by touchscreenelement lines is small, the chances of creating a visible moiré patternare greatly reduced. For example, a line that is only 5 micrometers widecannot substantially obscure an LCD color sub-pixel that is 100micrometers in diameter, resulting in little difference in visiblebrightness when the touchscreen element line overlaps a sub-pixel of theunderlying display. Nevertheless, even a high pixel-to-line dimensionratio touchscreen can exhibit subtle moiré banding effects under theright conditions, which might be objectionable.

The frequency or density of touchscreen lines is further a factor inproduction of moiré patterns, as greater spacing between lines orgreater differences in pitch between overlapping patterns generally tendto reduce likelihood of producing visible moiré patterns. Returning tothe example of FIG. 1, the example fingerprint 103 of approximately 8 mmcovers approximately four lines, resulting in a line pitch ofapproximately 2 mm between each line. When using fine line metaltouchscreen element electrodes that are 5 micrometers in width, thedistance between lines is approximately 400 times the width of thelines, resulting in a very low line density and a relatively large widthfrom line to line. Both the low density and relatively large spacingbetween lines reduce the likelihood of producing visible moiré patternswhen overlaying a display having a regularly repeating pixelconfiguration. In other examples, the line spacing is at least 20, 50,100, or 150 times greater than the line width.

The wavy and zig-zag lines in the examples shown include some repetitionin configuration of the lines, such as repeatedly going up and down inthe same pattern. The degree of repetition between adjacent lines isvaried in a further example, to further reduce the chances of creatingregular, repeating patterns that can contribute to moiré effects. Agroup of line elements such as 10, 20, 50, or some other suitable numberof lines is repeated in some embodiments to form larger touchscreens,reducing the work needed to lay out larger touchscreens having largenumbers of touchscreen electrode elements. Repetition of randomizedlines can be used where the repeated lines are sufficiently far apart orhave a sufficient number of non-repeating intervening lines as to beunlikely to contribute to moiré patterns, such as repeating every 10 or20 lines. A designer can therefore use a standard block of 20 randomlines and repeatedly use the same 20 lines to produce a largetouchscreen element array such as in FIG. 1, avoiding the need tomanually generate a large number of random lines for each application.

In some further examples, the scale of the line pattern is also takeninto consideration, such that the scale of repetition of the pixels ofthe underlying display is on a much smaller scale than the repetition ofthe anti-moiré touchscreen element pattern. For example, greensub-pixels on a touchscreen display may repeat every 100 microns, whilethe wavy line touchscreen electrode overlay repeats its pattern every 5millimeters. This difference in scale greatly reduces the chances ofobserving a moiré pattern, especially where the electrode line size issmall relative to the display's pixel size.

In other examples, the lines are random or semi-random in path, such asfractal-type lines shown at 204. These lines can be produced using avariety of methods including random number generation, use of fractalalgorithms, or can be drawn by hand.

Because it is desirable to keep adjacent lines from overlapping, and toknow the approximate position of the line for determining touchposition, line position in a further embodiment is restricted to acertain band or range. This can be achieved in a number of ways, such assimply setting upper and lower bounds for a randomization process,normalizing a generated line to fit within a certain band, changing theprobability of the next change in line direction based on line positionwithin a band to encourage reversion to a desired mean path, and othermethods. FIG. 2 shows at 206 an example of separately randomizedelectrode lines that are constrained within a certain band or range.

In addition to line direction, spacing between lines and repetition oflines can also be varied to reduce the regularity of the fine line metaltouchscreen element array, reducing the chances for observing moirépatterns. If the spacing between lines is varied, whether with randomlines such as fractal lines or repeating lines such as wavy lines, thelines will be significantly less likely to form regular repeatingpatterns of obscuring pixels on an underlying display, reducing thechances of moiré patterns being formed. As with randomizing linedirection, variation in line spacing can be achieved using a number ofsuitable techniques including randomization within a range,normalization of random numbers to a desired range, and other methods.Use of line constraints such as boundaries is again important inrandomizing line spacing to ensure that adjacent lines, such as the Xdrive lines and Y receive lines of FIG. 1, do not come too close ortouch one another, thereby causing field nonlinearities. FIG. 2 shows at207 one such example having variation of line position within a channel,and variation in frequency of repetition of line features.

FIG. 3 shows a two-layer touchscreen display assembly having randomizedtouchscreen element paths, such as is shown at 204 of FIG. 2. In thisexample, a first set of touchscreen elements 301 follow varyingrandomized paths so as to not form regular patterns of overlap with thepixels of an underlying display. Similarly, a second set of touchscreenelements 302 also follow varying randomized paths to avoid creatingmoiré patterns with the underlying display's pixels.

The lines 301 and 302 form a two-layer mutual capacitance touchscreenarray of drive and receive electrodes in a further example embodiment,much like the example of FIG. 1, but with significantly improvedimmunity to creation of moiré patterns. In an alternate embodiment, thearray of lines 301 and 302 form a self-capacitance touchscreen array, inwhich the self capacitance of the lines 301 and 302 are used todetermine the position of a touch on the two-dimensional touchscreen

As shown in the above examples, use of touchscreen electrode elementshaving complex or irregular patterns, irregular spacing, and othervariations can reduce moiré effect when the touchscreen overlays adisplay assembly having a regular repeating pattern of pixel elements.The examples of FIG. 2 can be easily applied to various touchscreenembodiments, such as the mutual capacitance and self capacitancetouchscreen examples presented above, as well as other touchscreenembodiments such as single-layer touchscreens.

FIG. 4 shows an arrangement of electrodes configured to form atouchscreen display, including overlapping mesh-like arrays ofelectrodes. Here, a first array of electrodes 401 are overlaid with asecond array of electrodes 402, such that the electrodes followirregular paths configured to avoid creating moiré patterns whenoverlaying a display. Although the electrodes are formed on differentlayers here, similar arrangements are used in other embodiments to formsingle layer touchscreen assemblies.

The touchscreen configuration shown here can be operated in one exampleas a mutual capacitance touchscreen, such as where the X lines are drivelines and the Y lines are receive lines. In another example, the X and Ylines are operated independently as self-capacitance electrodes.

In this example, the horizontal electrodes coupled to the X1 connectionare shown within the area of region 403, and the vertical electrodescoupled to the Y2 connection are shown within region 404. Region 405similarly shows the vertical electrodes coupled to connection Y3, and asection of the touchscreen display that overlaps these drive and receivesegments is shown at 406. A “dead zone” of vertical electrodes notcoupled to a vertical external connection are shown at 407 (denoted DZ),and are optionally included in various configurations in order toprovide improved linearity. As shown in the magnified vertical electrodeview at 408, the vertical dead zone Y electrode between the Y2 and Y3receive electrode regions is broken up in the vertical direction toprevent propagation of fields along the electrode axis, ensuring linearresponse of the touchscreen assembly.

The magnified vertical Y electrode view at 408 also illustrates how theY receive electrodes are formed in a mesh having a continuous pattern ofwavy lines that are interconnected with wavy line segments, with breaksthat separate the Y2 and Y3 electrode zones from the dead zone (DZ)electrode 407. These breaks are staggered here, to break up theregularity of separation between zones and prevent moiré patterns. The Ylayer electrodes are formed of a series of curves, but in otherembodiments are formed of polygons or other patterns. The S-shapedcurves forming the Y electrode pattern here further provide a degree ofredundancy in current path through the electrode, as the lines arebridged at regular intervals by crossing S-shaped curves to form themesh shown.

The Y electrode pattern shown in the magnified section shown at 408 isoverlaid in this example by the X electrode pattern shown at 409. The Xelectrode pattern includes an array of mixed parallelograms forming ahorizontal electrode mesh, with breaks between zones formed bytruncating ends of parallelograms and bridging the truncatedparallelograms as shown at 410. Bridging the truncated parallelogramshere prevents an open-ended line segment, providing greater conductivityand a redundant path for an undesired break or defect in theparallelograms. Further, vertices in the irregular parallelogramspattern shown at 409 are not in a straight line due to the variation inelectrode element angle and mixed parallelogram shapes. Breaks betweenparallelograms at their vertices to form the breaks between zonestherefore vary in position as shown at 410, reducing the chances ofmoiré effect and providing some degree of interpolative effect betweenzones.

Different shapes and shape variations may be used to form the mixedparallelogram array depending on the requirements of a particularapplication, for example pixel pitch, electrode spacing, required linedensity, and so on. Use of line elements having fewer than fourdifferent angles, such as a regular checkerboard pattern, can be used insome examples but may contribute to a greater likelihood of producing amoiré effect. It has been shown that a mix of parallelograms has thepotential advantage of having many non-orthogonal line angles whilebeing readily scaleable in density and pitch. Other shapes, such varioustypes of polygons, curves, random or semi-random lines, and other suchelectrodes can be used in addition to the parallelograms shown,including in various combinations, and are within the scope of theinvention.

The electrodes shown at 408 and 409 are overlaid in the enlarged viewshown at 411, illustrating how the two electrode patterns are layeredtogether with electrical isolation between them (not shown) to form apattern of electrodes as shown generally in FIG. 4 at 400. The Xelectrode polygons and the Y electrode S-curves are configured to formmeshes with elements that have the same pitch, and repeat at the samefrequency in both dimensions. This enables the intersections of polygonsin the X electrode layer to be placed in the open spaces formed by theS-curves of the Y electrode pattern, and the intersections betweens-curves of the Y electrode pattern are located in the open spacesformed by the polygons of the X electrode layer.

Further, the many crossovers between X electrodes and Y electrode tracesor wires when overlaid and viewed from above are approximatelyorthogonal, reducing the change in sensitivity of the touchscreen tosmall alignment changes or imperfections in the layer-to-layer assemblyprocess. Oblique angles can cause pattern displacement errors duringassembly which can cause substantial field non-linearities, and so it isdesirable to reduce this form of error. In various further examples, thecrossover angle between drive and receive elements is desirably at least45 degrees, 60 degrees, or another suitable angle to manage thesensitivity of the touchscreen to pattern alignment.

Fine line patterns exhibit localized field fluctuations due to patterngranularity, which apart from layer to layer alignment errors causesregional fluctuations in sensitivity. It is desirable to align thesefluctuations in a regular way, synchronized if possible with electrodecenterlines. The electrode pattern here is configured such that thepitch of the electrode connections such as Y1 and Y2 align with thepitch of repetition of the Y mesh, and the pitch of the electrodeconnections X1 and X2 align with the pitch of the X electrode mesh. Themeshes in each layer are thus repeating along each axis, insynchronicity with the electrode centers. This ensures that theelectrode mesh's relation to the electrode connections is the same ateach electrode connection, providing good linearity in geometry andresponse between electrode regions.

Construction of the touchscreen example of FIG. 4 in one exampleincludes fabrication of the X and Y electrode layers on separate plasticsheets, and lamination of the sheets under a cover lens. In anotherexample, the X and Y layers are fabricated on the same plastic sheet orother substrate, with a dielectric material printed or deposited at thecrossover points between electrodes to prevent conduction between X andY layers.

The X drive and Y receive layers in FIG. 4 can be easily reversed, sothat either of the X or Y layer is the drive or receive layer, with nosignificant change in the performance of the touchscreen assembly. Inanother example, the same pattern or mesh is used for the X and Ylayers, such as using S-curves for both the X and Y layers or usingpolygons for both the X and Y layers. The net effect of any suchconfiguration is that a touchscreen electrode pattern with no apparentmoiré effect is provided.

In various touchscreen configurations, the electrodes of FIG. 1 are madeof various materials such as indium tin oxide, conductive polymer, ornarrow metal lines. Fine metal wires in a more detailed example compriseprinted metal traces that are approximately 10 micrometers or less inwidth, or another similar suitable size such as under 20 micrometers orunder 5 micrometers in width. A more detailed example includes fine linemetal lines that are approximately 10 micrometers in width, and occupy3-7% of the total screen area. The very small line width enablesplacement of many lines per millimeter in some embodiments, as the totalline density can in various embodiments cover a fraction of a percent to10% of the total screen area without significantly impacting thevisibility of an image through the touchscreen.

FIG. 5 shows the field lines associated with an electrode withself-capacitive coupling. Here, field lines extend from an electrodeline 501 (shown as X) operated by a circuit 502, the fields penetratingthrough panel 503. A portion of the emitted field 504 escapes into freespace or other parts of the panel as shown, and capacitively coupleswith a finger when present. The circuit 502 observes a change inself-capacitance of electrode 501 due to the presence of a finger nearfield lines 504, such as by observing a greater charge is needed tochange the voltage of the electrode 501. A great many forms ofcapacitive sensor circuit exist in the art and are well known, which canbe used for circuit 502.

FIG. 6 shows an electrode configuration with mutual capacitive coupling.Here, a finger 601 causes field lines 602 normally coupling from driveelectrode 603 to receive electrode 604 as shown at 606 to be absorbed bythe finger 601. The result of this action is a very detectable decreasein signal level by receiver 605, the reduction in signal being relatedto a variety of factors such as fingerprint area, electrode area, panel607 thickness and dielectric constant, human body size and location,skin thickness and conductivity, and other factors.

FIG. 7 shows one physical implementation of a single electrode layerstack over a display such as an LCD. The electrodes 701 are printed orotherwise fashioned onto a substrate 702, which in some embodiments is aclear plastic sheet such as PET or polycarbonate, or potentially a glasslayer. Adhesive 703 is used to bond substrate layer 702 to panel 704;adhesive 703 is in some embodiments a liquid adhesive, or an adhesivesheet. Assembly may be via a laminating process to provide for anairtight assembly. Electrodes 701 may be fashioned from clear ITO, fineline metal traces, or other low visibility conductive material when usedwith a display. If no display is used, then the optical properties ofassembly 705 are not relevant and any set of suitable materials may beused. Gap 706 is an airgap between the display and the assembly 705, asis common in the art. In some cases it is advantageous to insert anadhesive layer in this gap and laminate the entire stack to the top ofthe display.

FIG. 8 shows an assembly stack 801 which contains two sensing layers,for example as may be used to implement the design of FIG. 4. Two layersof plastic film are used, 802 and 803, with respective electrodes 804and 805 fashioned thereon, and assembled with adhesive layers 806, 807and optionally 808 via a lamination process to panel 809 and possiblyalso to display 810.

FIG. 9 shows the layer stack of FIG. 8 as laminated together, butwithout the adhesive layer 808, using instead an airgap 901.

Touchscreens are often used in a variety of applications, from automaticteller machines (ATM machines), home appliances, personal digitalassistants and cell phones, and other such devices. One such examplecellular telephone or PDA device is illustrated in FIG. 10. Here, thecellular telephone device 1001 includes a touchscreen display 1002comprising a significant portion of the largest surface of the device.The large size of the touchscreen 1002 enables the touchscreen topresent a wide variety of images that can serve along with touchscreencapability to provide input to the device, including a keyboard, anumeric keypad, program or application icons, and various otherinterfaces as desired.

The user may interact with the device by touching with a single finger,such as to select a program for execution or to type a letter on akeyboard displayed on the touchscreen display assembly 1002, or may usemultiple touches such as to zoom in or zoom out when viewing a documentor image. In other devices, such as home appliances, the display doesnot change or changes only slightly during device operation, and mayrecognize only single touches.

Although the example touchscreen display of FIG. 10 is configured as arectangular grid, other configurations are possible and are within thescope of the invention, such as a touchwheel, a linear slider, buttonswith reconfigurable displays, and other such configurations.Proportionate distribution of drive or receive electrodes coupled todifferent elements across the touchscreen element can be adapted to anysuch shape, enabling detection of the region of input on thetouchscreen.

Many materials and configurations will be suitable for formingtouchscreens such as those described herein, including printed or etchedfine line metal, metal wire, Indium tin oxide (ITO), conductivepolymers, and other such materials.

These example touchscreen assemblies presented here illustrate how atouchscreen can be formed using electrodes configured to reduce theprobability of creating a visible moiré pattern when overlaying adisplay having a repeating pattern of pixels. Although the anti-moirétouchscreen display assembly examples given here generally rely onmutual capacitance or self-capacitance to operate, other embodiments ofthe invention will use other technologies, including other capacitancemeasures, resistance, or other such sense technologies. This applicationis intended to cover any adaptations or variations of the exampleembodiments described herein, and this invention is limited only by theclaims, and the full scope of equivalents thereof.

1. An apparatus comprising: an adhesive layer between a cover panel anda substrate; and the substrate, with drive or sense electrodes of atouch sensor disposed on it, the drive or sense electrodes being made ofa conductive mesh of conductive material comprising metal.
 2. Theapparatus of claim 1, wherein the conductive mesh comprises a pluralityof mesh segments, each of the mesh segments having a width ofapproximately 10 μm.
 3. The apparatus of claim 1, wherein each of themesh segments is substantially sinusoidal.
 4. The apparatus of claim 1,further comprising a display separated from the substrate by adielectric layer.
 5. The apparatus of claim 4, wherein the dielectriclayer comprises an air gap.
 6. The apparatus of claim 4, wherein thedielectric layer comprises an adhesive layer.
 7. The apparatus of claim1, wherein the substrate is polyethylene terephthalate (PET), glass, orpolycarbonate (PC).
 8. The apparatus of claim 1, wherein the adhesivelayer is an optically clear adhesive (OCA).
 9. An device comprising: acover panel; an adhesive layer between the cover panel and a substrate;the substrate, with drive or sense electrodes of a touch sensor disposedon it, the drive or sense electrodes being made of a conductive mesh ofconductive material comprising metal; and one or more computer-readablenon-transitory storage media embodying logic that is configured whenexecuted to control the touch sensor.
 10. The device of claim 9, whereinthe conductive mesh comprises a plurality of mesh segments, each of themesh segments having a width of approximately 10 μm.
 11. The device ofclaim 9, wherein each of the mesh segments is substantially sinusoidal.12. The device of claim 9, further comprising a display separated fromthe substrate by a dielectric layer.
 13. The device of claim 12, whereinthe dielectric layer comprises an air gap.
 14. The device of claim 12,wherein the dielectric layer comprises an adhesive layer.
 15. The deviceof claim 9, wherein the substrate is polyethylene terephthalate (PET),glass, or polycarbonate (PC).
 16. The device of claim 9, wherein theadhesive layer is an optically clear adhesive (OCA).
 17. An apparatuscomprising: an adhesive layer between a cover panel and a substrate; thesubstrate, with electrodes of a touch sensor disposed on it, theelectrodes being made of a conductive mesh of conductive materialcomprising metal; and a display separated from the substrate by anadhesive layer.
 18. The apparatus of claim 17, wherein the substrate ispolyethylene terephthalate (PET), glass, or polycarbonate (PC).
 19. Theapparatus of claim 17, wherein the conductive mesh comprises a pluralityof mesh segments, each of the mesh segments having a width ofapproximately 10 μm.
 20. The apparatus of claim 17, wherein the adhesivelayer is an optically clear adhesive (OCA).